1. Field of the Invention
The present invention relates generally to lamps for motor vehicles and more particularly to direct current light-emitting diode (LED) lamps and more particularly to LED lamp modules containing control circuitry for producing light of high intensity usable as a tail, brake, or turn signal lamp.
2. Background
The features of the present invention are particularly useful as applied to the construction of LED lamp modules to replace incandescent lamps used in automobiles and other motor vehicles and are applicable to the manufacture of LED replacement bulbs for both single filament and dual filament incandescent bulbs. LED""s typically operate at voltages between 1.7 and 2.2 volts. Overvoltaging and overheating of LED""s result in significant degradation of the performance and lifetime of LED""s. One well known type of existing incandescent lamp generally employs a type S-8 glass bulb cemented in a double-contact brass bayonet base. A second type of incandescent lamp has a similar bulb inserted into an insulated plastic wedge base that is adapted to fit into a corresponding plastic socket. A type of incandescent bulb with a wedge base is described in U.S. Pat. No. 4,603,278 (Devir et al.). Incandescent vehicle signal-lamp bulbs consume a relatively large amount of power, generate a large amount of heat and have a relatively short life.
LED bulbs designed to replace vehicle incandescent bulbs require bases similar to the standard bayonet or the wedge bases. To be effective an LED bulb must be adapted to produce an intense light when viewed by the human eye and must provide for effective heat dissipation to avoid impairing the LED""s. It also must be designed to operate within the range of voltages present in motor vehicles so as to not over-voltage the LED""s. Finally, some models of motor vehicles ground the brake circuit when the brake is not activated to prevent any accidental activation of the brake lights; accordingly, an effective LED bulb designed to replace a dual filament bulb must contain circuitry enabling the LED""s to be activated with either the tail lamp circuit or the brake light circuit.
One approach to solving the problems of cooling the LED""s is given in U.S. Pat. No. 5,632,551 (Roney et al.) which describes an LED bulb as used in truck trailers and/or tractors. The LED""s are mounted on a printed circuit board (PCB). The LED""s are embedded in resin to facilitate the conduction of heat away from the LED""s so that the heat will not cause the LED""s to degrade and lose brightness. This bulb is not designed to fit in standard automotive lamp sockets.
A second approach to the cooling problem is given by U.S. Pat. No. 5,575,459 (Anderson) which describes an AC LED bulb that uses air holes to provide air circulation and cooling for an LED bulb. This bulb is not suitable for motor vehicle use.
U.S. Pat. No. 6,045,240 (Hochstein) presents a third solution to the problem of cooling the LED""s by teaching the use of a heat sink to cool an LED array. This is not a bulb, but a lamp assembly; therefore it is not suitable for replacing an incandescent light bulb.
One type of LED bulb with a wedge base is described in U.S. Pat. No. 5,160,200 (Cheselske). It provides a parallel string of LED""s soldered and rolled up for 2-volt dc operation. The roll is placed in a housing with two leads extending out the wedge type base. No provisions are made for 12-volt operation, dual element operation, voltage control, heat dissipation, or brightness enhancement. The wedge is not suitable for motor vehicle wedge type sockets, because it differs in size and shape from the automotive standard. Additionally, it does not have the required fasteners for motor vehicle applications. It is also limited in the number of LED""s which may be contained and therefore the brightness because of the cylindrical shape specified for the body. A funnel shaped body is more desirable for automotive applications. Typical LED""s are 1.7 to 2.2 volts dc. If this bulb were connected to vehicle voltage of 12 to 14 volts dc, the LED""s will burn out.
U.S. Pat. No. 5,947,588 (Huang) describes an LED bulb where an LED array is mounted on a printed circuit board which is in turn mounted on a standard automotive bayonet type base. The LED""s are directly connected to the electrical contacts on the bayonet base. The patent shows an embodiment of the bulb to replace a dual filament bulb. The patent does not describe the circuit connections of the LED""s to the contacts, but either the LED""s are grouped into two sets-one for use as tail lights and a second for use as brake lightsxe2x80x94or the LED""s are connected in parallel so that all LED""s are illuminated when either the tail light or the brake light circuit is energized. If the LED""s are grouped in the two sets then all of the LED""s cannot be energized at once resulting in dimmer tail light and brake lights. On the other hand, if the circuits are connected in parallel so that all LED""s would be energized if either tail lamp or brake lamp circuit were energized, the array would not work as tail lamps in automobiles in which the brake lamp is grounded when the brake is not activated. Also, if this configuration did work in some vehicles, the tail lamps and the brake lamps would be illuminated with equal intensity, that is the brake lights would not be brighter. The patent discusses the problem of low intensity by suggesting the addition of more LED""s; this would make the array larger than a standard incandescent lamp which in turn would result in the LED lamp being unable to fit into many tail lamp assemblies. Also, this configuration of LED bulb will not fit into many recessed automotive sockets and lamp assemblies.
Voltage varies from vehicle to vehicle from a low of 10-volts to high of 14.5 volts. In the LED bulb of U.S. Pat. No. 5,947,588, the LED""s will dim in low voltage situations or worse, burn out in over voltage situations, both of which are undesirable. No means is provided for controlling the voltage and current. This lack of control causes the brightness to vary according to the vehicle voltage. It is well known that most vehicles"" batteries are 12-volts dc when fully charged. They are less than 12 volts when undercharged. Most vehicles charging systems produce in excess of 12-volts dc and typically between 13 and 14 volts. With applied voltage spread evenly divided across a plurality of LED""s in the instant bulb without control circuitry there will be a very noticeable difference in brightness at low voltage situations and in over voltage condition on the LED""s at the higher voltage extreme. Whereas incandescent bulbs are not susceptible to damage due to said over voltage situations nor do they dim down excessively at under voltage conditions, LED""s by nature lose brightness disproportionately to the reduced voltage when operated below their typical specified operating voltage. On the other hand, LED""s can only handle their specified maximum voltage without degradation or failure.
It is desirable to produce a light bulb that has a plurality of light-emitting diodes (LED""s) which can be illuminated all at once and in a controlled way so as to have a different brightness for brake and tail light applications connected to a conventional bayonet or plastic wedge-type base so as to replace conventional single or dual filament incandescent bulbs. Neither U.S. Pat. No. 5,160,200 (Cheselske) nor U.S. Pat. No. 5,947,588 (Huang) provide a way of controlling the brightness of the LED array in different applications.
It is an object of the present invention to provide an LED replacement bulb for incandescent light bulbs, which is adapted for use in all standard vehicle sockets.
It is further an object of the present invention to provide an LED replacement bulb for incandescent light bulbs, which will protect the LED""s from degradation due to overheating.
It is further an object of the present invention to provide an LED replacement bulb for incandescent light bulbs, which will protect the LED""s form degradation due to overvoltage or excess current.
It is still further an object of the present invention to provide an LED replacement bulb for incandescent light bulbs, which will give greater brightness as sensed by the human eye.
It is further an object of the present invention to provide an LED replacement bulb for incandescent light bulbs with integrated dual element control of the entire plurality of LED""s.
It is further an object of the present invention to provide an LED replacement bulb for incandescent light bulbs with integrated dual element control of the entire plurality of LED""s.
It is further an object of the present invention to provide an LED replacement bulb for incandescent light bulbs with a means for pulsating the LED array so as to increase brightness output, reliability, and life expectancy while reducing energy consumption, heat, and resulting degradation of the LED""s.
It is further an object of the present invention to provide an LED replacement bulb for incandescent light bulbs that has no ramp-up time for light intensity as the incandescent bulbs have.
It is still further an object of the invention to provide a bulb to employ a standard bayonet and wedge base for easy and cost effective production.
These and other objects, advantages, and features are attained, in accordance with the principles of this invention by an LED array connected to control circuitry. In one embodiment, a replacement for a dual filament bulb, the problem of controlling the intensity of the light emitted by the array is solved by having a first resistor in series with the array connected to the tail light connection on the bulb base. This controls the intensity and prevents overvoltaging and overheating by controlling the voltage and current to the array. A second resistor and a diode are connected in series with the array to the brake light connection on the bulb base. The diode prevents the array from being grounded when the brake light connection is grounded in some vehicles, while the second resistor provides for a higher voltage and current to be applied to the LED array resulting in greater intensity of the emitted light.
Another embodiment solves the problems of controlling the brightness of the LED array by energizing the LED""s with a series of pulses of higher voltage but short duration. For a pulse frequency of 50 Hz or greater the human eye, due to persistence of the image, will see the pulse as a constant intense light. The individual pulses of light have much higher intensity than when a constant voltage is applied to the LED array. However, since the pulses are of very short duration, the total power consumption is less than with a constant voltage solving the problem of overheating the LED""s. The pulse circuitry also prevents the degradation of the LED""s due to over-voltage by controlling the duty cycle appropriately.
In order to provide a universal replacement for incandescent vehicle bulbs they are packaged in a configuration that mimics the size and shape of the original bulb. Other provisions in the design provide for cooling of electronics and use with a standard bayonet or wedge base as are found on bulbs.
The present invention is a unique light emitting diode vehicle lamp module adapted for mounting in standard vehicle brake/tail lamps or turn signal assemblies to replace standard vehicle incandescent bulbs. The invention features universal vehicle fit, integrated dual element control, voltage and current regulation, brightness, enhancement circuitry, improved energy efficiency, and longer life expectancy. It features a base adapted to fit a standard vehicle lamp assembly and further adapted to make electrical connection with said brake/tail lamps or turn signal assembly, circuitry electrically connected to said base to control and enhance brightness a plurality of light emitting diodes, a light emitting diode cluster mounted on a printed circuit card or otherwise electrically connected and mounted in a wedge or bayonet base which encases the said control and brightness circuitry so said light emitting diodes illuminate when an electrical signal is applied to said motor vehicle lamp assembly and where said light emitting diode cluster is aligned to shine directly through the lens of the tail lamp or turn signal assembly. The present invention differs from the prior art in that all LED""s are illuminated for both tail and brake light circuits, but with different controlled light intensities.